1. Field of the Invention
The present invention relates to a high-frequency module that includes a switch integrated circuit (IC) and that transmits and receives a plurality of communication signals in a switching manner.
2. Description of the Related Art
Hitherto, various high-frequency modules that transmit and receive a plurality of communication signals using a common antenna have been suggested. In such a high-frequency module, it is necessary to connect terminals to which a plurality of communication signals are input or from which a plurality of communication signals are output to an antenna in a switching manner. Thus, for example, the high-frequency module described in Japanese Unexamined Patent Application Publication No. 2008-271420 includes a switch IC. A common terminal of the switch IC is connected to an antenna connection terminal of the high-frequency module. A plurality of switch terminals which are connected to the common terminal of the switch IC in a switching manner are respectively connected to individual input/output terminals of the high-frequency module.
In such a high-frequency module including a switch IC, a matching circuit for achieving impedance matching between a common terminal of the switch IC and an antenna may be provided between the switch IC and an antenna connection terminal.
An example of such a matching circuit is a band-pass-filter-type matching circuit including an inductor which is connected in series between a common terminal of a switch IC and an antenna connection terminal of a high-frequency module in order to cancel the off capacitance of the switch IC. The band-pass-filter-type matching circuit is formed of a low pass filter and a high pass filter.
Also, a matching circuit is provided between each input/output terminal and a corresponding switch terminal.
However, with a trend of increased utilization of a multiband scheme for high-frequency modules, the frequency band of communication signals which are transmitted and received in a switching manner using a switch IC has become wider. Furthermore, with the decreasing size of communication terminals provided with high-frequency modules, there have been demands for further decreases in the size and height of high-frequency modules. Accordingly, there have been demands for further decreases in the size and height of individual elements included in high-frequency modules.
Therefore, a matching circuit according to the related art may be incapable of achieving sufficient impedance matching for all communication signals used in a high-frequency module. Accordingly, desired transmission characteristics are not always acquired between a common terminal and a specific input/output terminal. This is because a component such as a parasitic capacitance between a common terminal of a switch IC and an antenna connection terminal connected to the common terminal affects the impedance characteristics between the common terminal and the input/output terminal.
For example, in a case where impedance matching is performed with a band pass filter including a series-connected inductor as described above, cancelling of an off capacitance causes an inductance value to increase. Accordingly, in some cases, impedance matching is not achieved for a communication signal of a high-frequency band.
Also, in order to achieve matching in a specific frequency band, it is necessary to set a large capacitance of a capacitor which connects one end of an inductor providing the above-described band pass filter to a ground. However, a large capacitance may cause a decrease in cutoff frequency of a low pass filter providing the band pass filter. Accordingly, the insertion loss on the high-frequency side of the specific frequency band increases, and desired characteristics are not obtained in some cases.